Papers by Alessandra Padiglia
Euphorbia characias copper/zinc superoxide dismutase mRNA, partial cds
Plants, 2020
Polyphenol oxidase (PPO, E.C. 1.14.18.1) is a nearly ubiquitous enzyme that is widely distributed... more Polyphenol oxidase (PPO, E.C. 1.14.18.1) is a nearly ubiquitous enzyme that is widely distributed among organisms. Despite its widespread distribution, the role of PPO in plants has not been thoroughly elucidated. In this study, we report for the absence of PPO in Cynomorium coccineum, a holoparasitic plant adapted to withstand unfavorable climatic conditions, growing in Mediterranean countries and amply used in traditional medicine. The lack of PPO has been demonstrated by the absence of enzymatic activity with various substrates, by the lack of immunohistochemical detection of the enzyme, and by the absence of the PPO gene and, consequently, its expression. The results obtained in our work allow us to exclude the presence of the PPO activity (both latent and mature forms of the enzyme), as well as of one or more genes coding for PPO in C. coccineum. Finally, we discuss the possible significance of PPO deficiency in parasitic plants adapted to abiotic stress.
A copper-and zinc-containing superoxide dismutase (Cu/Zn-SOD) cDNA was isolated from the Euphorbi... more A copper-and zinc-containing superoxide dismutase (Cu/Zn-SOD) cDNA was isolated from the Euphorbia characias latex (Elx) using consensus degenerate hybrid oligonucleotide primer (CODEHOP) design and RT-PCR strategy. Both 3'and 5'untraslated regions (UTR) were isolated by rapid amplification of cDNA ends (RACE) method. Analysis of the nucleotide sequence revealed that the Cu/Zn-SOD cDNA contains an open reading frame encoding a protein of 152 amino acids. Bioinformatic analyses of Elx SOD gene revealed a high identity rate with a large number of plant Cu/Zn-SODs in the deduced amino acid sequence. Since isoenzymes may be generated through the multiplicity of SOD genes or result from post-trascriptional events, genomic Southern blot in conjunction with northern blot experiments were also performed. The genomic analysis showed that the E. characias genome contains a single SOD gene. Northern blot analyses confirmed the presence of a single SOD mRNA demonstrating that alternative splicing does not occur. Quantitative real time-PCR (qRT-PCR) experiments showed that SOD gene expression in latex reaches maximum levels during the summer. These results suggest that the Cu/Zn-SOD of Euphorbia characias latex probably may be involved in the antioxidative process triggered by oxidative stress induced by the conditions of environmental change in which the plant lives.
Biochimica Et Biophysica Acta-general Subjects, 2011
Backgroundo-Aminophenols have been long recognised as tyrosinase substrates. However their exact ... more Backgroundo-Aminophenols have been long recognised as tyrosinase substrates. However their exact mode of interaction with the enzyme's active site is unclear. Properly vic-substituted o-aminophenols could help gain some insight into tyrosinase catalytic mechanism.
Polymorphisms in TAS2R38 and the taste bud trophic factor, gustin gene co-operate in modulating PROP taste phenotype
Physiology & Behavior, 2011
The PROP taste phenotype varies greatly among individuals, influencing eating behavior and theref... more The PROP taste phenotype varies greatly among individuals, influencing eating behavior and therefore may play a role in body composition. This variation is associated with polymorphisms in the bitter receptor gene TAS2R38 and the taste-bud trophic factor gustin gene. The aim of this study was to examine the relationship between TAS2R38 haplotypes and the gustin gene polymorphism rs2274333 in modulating PROP taste phenotype. PROP phenotype was determined in seventy-six volunteers (29 males, 47 females, age 25±3 y) by scaling methods and threshold measurements. TAS2R38 and gustin gene genotyping was performed using PCR techniques. The lowest responsiveness in PROP nontasters is strongly associated with the AVI nontasting TAS2R38 variant and the highest responsiveness in supertasters is strongly associated to allele A and genotype AA of the gustin gene. These data support the hypothesis that the greater sensitivity of supertasters could be mediated by a greater taste-bud density. Polymorphisms in TAS2R38 and gustin gene, together, accounted for up to 60% of the phenotypic variance in PROP bitterness and to 40% in threshold values. These data, suggest that other unidentified factors may be more relevant for detecting low concentrations of PROP. Moreover, the presence of the PAV variant receptor may be important for detecting high concentrations of PROP, whereas the presence of allele A in gustin polymorphism may be relevant for perceiving low concentrations. These data show how the combination of the TAS2R38 and gustin gene genotypes modulate PROP phenotype, providing an additional tool for the evaluation of human eating behavior and nutritional status.
American Journal of Clinical Nutrition, 2010
Background: The individual ability to taste 6-n-propylthiouracil (PROP) may be correlated with bo... more Background: The individual ability to taste 6-n-propylthiouracil (PROP) may be correlated with body mass index (BMI) and differences in the salivary proteins involved in taste function, such as the zinc-dependent enzyme gustin, which is a trophic factor of taste buds. Objective: We investigated the possible association of PROP taste responsiveness with gustin gene polymorphism rs2274333 (A/G), salivary ionic zinc concentrations, and BMI. Design: We measured cognitive eating behaviors and BMI in 75 volunteers (28 men and 47 women; mean 6 SEM age: 25 6 3 y). The intensity of taste perception evoked by PROP and sodium chloride solutions was estimated to evaluate PROP taster status. Salivary ionic zinc concentrations were measured, and molecular analyses of the gustin gene polymorphism were performed in individuals classified by PROP status by using polymerase chain reaction techniques. Results: We classified subjects as PROP supertasters (n = 27), medium tasters (n = 28), or nontasters (n = 20). Salivary ionic zinc concentrations and BMI were greater in nontasters than in supertasters (P = 0.003 and P = 0.042, respectively). Molecular analyses of gustin DNA showed that allele A and genotype AA were significantly more frequent in supertasters, whereas allele G and genotype GG were significantly more frequent in nontasters (P , 0.001). Conclusions: These data showed that responsiveness to PROP is inversely related to BMI and salivary ionic zinc concentrations. The gustin gene dimorphism rs2274333 observed in supertaster and nontaster subjects may influence the protein conformation and, thereby, affect zinc ion binding. Our data showed a direct association between PROP sensitivity and a polymorphism in the gustin gene that is hypothesized to affect its function. This trial was registered at clinicaltrials.gov as UNICADBSITB-1.
International Journal of Biological Macromolecules, 2005
The changes in the heme environment and overall structure occurring during reversible thermal ina... more The changes in the heme environment and overall structure occurring during reversible thermal inactivation and in denaturant guanidinium of Euphorbia characias latex peroxidase (ELP) were investigated in the presence and absence of calcium ions. Native active enzyme had an absorption spectrum typical of a quantum-mixed spin ferric heme protein. After 40 min at 60 • C ELP was fully inactivated showing the spectroscopic behavior of a pure hexacoordinate low-spin protein. The addition of Ca 2+ to the thermally inactivated enzyme restored its native activity and its spectroscopic features, but did not increase the stability of the protein in guanidinium. It is concluded that, in Euphorbia peroxidase, Ca 2+ ion play a key role in conferring structural stability to the heme environment and in retaining active site geometry. (R. Medda). found in the cytosol, vacuole, apoplast or cell wall, and are involved in the regulation of cell growth and differentiation, cell wall lignification, metabolism of hormones and alkaloids, wound healing and defense against pathogen infection . Typically, class III peroxidases may exist under an extremely high number of isoforms within the same species, potentially implicated in different functions . For example, the peroxidase isoenzyme family of Arabidopsis thaliana comprises over 70 full-length genes, most of which predicted to encode for stable enzymes .
Phytochemistry, 1995
In this review, the widely distributed plant copper-amine oxidases are described. The purificatio... more In this review, the widely distributed plant copper-amine oxidases are described. The purification procedures, molecular features, substrate specificities, inhibitors, the stoichiometry of the catalysed reaction, spectroscopic features, the prosthetic groups and reaction mechanisms, are all reviewed. \
Biochemistry, 2005
Calmodulin (CaM) is a ubiquitous Ca 2+ sensor found in all eukaryotes, where it participates in t... more Calmodulin (CaM) is a ubiquitous Ca 2+ sensor found in all eukaryotes, where it participates in the regulation of diverse calcium-dependent physiological processes. In response to fluctuations of the intracellular concentration of Ca 2+ , CaM binds to a set of unrelated target proteins and modulates their activity. In plants, a growing number of CaM-binding proteins have been identified that apparently do not have a counterpart in animals. Some of these plant-specific Ca 2+ /CaM-activated proteins are known to tune the interaction between calcium and H 2 O 2 in orchestrating plant defenses against biotic and abiotic stresses. We previously characterized a calcium-dependent peroxidase isolated from the latex of the Mediterranean shrub Euphorbia characias (ELP) Biochemistry 42, 8909-8918].
The reaction mechanism of copper amine oxidase: detection of intermediates by the use of substrates and inhibitors
Biochemistry, 1995
Intermediate states in the catalytic mechanism of lentil copper amine oxidase have been investiga... more Intermediate states in the catalytic mechanism of lentil copper amine oxidase have been investigated by ESR and optical spectroscopy. Using highly purified apo- and holoenzyme in combination with a poor substrate and a range of inhibitors, under both aerobic and anaerobic conditions, the single steps of the reaction mechanism can be slowed down or 'frozen' completely. In this way, a sequence of six intermediate species in the catalytic cycle has been established. Oxidative deamination of p-(dimethylamino)benzylamine is 5 x 10(5) times slower than for putrescine; the rate-limiting step is shown to be release of the aldehyde product. This process is not affected in the apoenzyme, but subsequent intramolecular electron transfer to form the characteristic free radical intermediate is completely blocked, and the apoenzyme is trapped as an aminoresorcinol species. Classic hydrazine and hydrazide inhibitors bind to the 6-hydroxydopa cofactor in the same way as active substrates, but rearrangements lead to formation of stable intermediate adducts at the step preceding release of aldehyde. The semicarbazide-6-hydroxydopa adduct is shown to bind simultaneously to Cu(II), providing the first direct evidence for localization of 6-hydroxydopa close to the copper site.
A copper-containing amine oxidase from the latex of Euphorbia characias was purified to homogenei... more A copper-containing amine oxidase from the latex of Euphorbia characias was purified to homogeneity and the copper-free enzyme obtained by a ligand-exchange procedure. The interactions of highly purified apo-and holoenzyme with several substrates, carbonyl reagents, and copper ligands were investigated by optical spectroscopy under both aerobic and anaerobic conditions. The extinction coefficients at 278 and 490 nm were determined as 3.78 ؋ 10 5 M ؊1 cm ؊1 and 6000 M ؊1 cm ؊1 , respectively. Active-site titration of highly purified enzyme with substrates and carbonyl reagents showed the presence of one cofactor at each enzyme subunit. In anaerobiosis the native enzyme oxidized one equivalent substrate and released one equivalent aldehyde per enzyme subunit. The apoenzyme gave exactly the same 1:1:1 stoichiometry in anaerobiosis and in aerobiosis. These findings demonstrate unequivocally that copper-free amine oxidase can oxidize substrates with a single half-catalytic cycle. The DNA-derived protein sequence shows a characteristic hexapeptide present in most 6-hydroxydopa quinonecontaining amine oxidases. This hexapeptide contains the tyrosinyl residue that can be modified into the cofactor 6-hydroxydopa quinone.
Iubmb Life, 1997
Spermine is a substrate of lentil seedling amine oxidase and is oxidized at terminal amino groups... more Spermine is a substrate of lentil seedling amine oxidase and is oxidized at terminal amino groups to a dialdehyde: 2 mot of hydrogen peroxide and two mol of ammonia per mol of spermine are formed. In the presence of hight amounts of spermine, the aldehydic groups formed upon oxidation of spermine by the enzyme, may react with primary amino groups of free spermine leading to the formation of aromatic pyrimidinic ring after β-elimination at secondary amino groups.
Phytochemistry, 1995
Key Word Index--Opuntiaficus indica; Cactaceae; peroxidase; hydrogen peroxide; plant hemoprotein.
Fractionation and Characterization of Two Forms of Peroxidase from Oryza Sativa
Preparative Biochemistry & Biotechnology, 1995
Peroxidase (E.C. 1.11.1.7., hydrogen donor oxidoreductase) is widely distributed and has been iso... more Peroxidase (E.C. 1.11.1.7., hydrogen donor oxidoreductase) is widely distributed and has been isolated from many higher plants (1). The wide distribution of the enzyme suggests that it could be of great biological importance. However the role that it plays in metabolism is not clear due to the large number of reactions it catalyzes and the considerable number of isozymic species (2). In tomato plants, Evans and Aldridge (3) separated out six isoperoxidases and in a later paper Evans reported 12 isoperoxidases from tomato shoots (4). A homogeneous tomato fruit peroxidase isozyme was obtained by Jen et al. (5) using hydrophobic chromatography. Isozymes were not detected in Euphorbia characias peroxidase (6), in Ipomoea batatas peroxidase (7) and in Hordeum vulgare peroxidase (8). The simultaneous presence of Cu (II) amine oxidase and peroxidase in cell walls suggests that the peroxide generated on oxidation of the amines could be utilized by the peroxidase (6,8,9). In the graminea Oryza sativa, widely distributed, an FAD amine oxidase is present that oxidizes diamines (10). In this plant we also found two isoperoxidases called perox I and II. Only perox I was purified to homogeneity and its enzymatic, physical and chemical properties have been studied.
An unexpected formation of the spectroscopic Cu I-semiquinone radical by xenon-induced self-catalysis of a copper quinoprotein
Biochimie, 2006
Plant copper/quinone amine oxidases are homodimeric enzymes containing Cu(II) and a quinone deriv... more Plant copper/quinone amine oxidases are homodimeric enzymes containing Cu(II) and a quinone derivative of a tyrosyl residue (2,4,5-trihydroxyphenylalanine, TPQ) as cofactors. These enzymes catalyze the oxidative deamination of primary amines by a classical ping-pong mechanism, i.e. two distinct half-reactions, enzyme reduction by substrate followed by its re-oxidation by molecular oxygen. In the first half-reaction two forms of the reduced TPQ have been observed, the colorless Cu(II)-aminoquinol and the yellow Cu(I)-semiquinolamine radical so that this enzyme may be referred to as a "protein-radical enzyme". The interaction of xenon, in aqueous solutions, with the copper/TPQ amine oxidase from lentil (Lens esculenta) seedlings has been investigated by NMR and optical spectroscopy. NMR data indicate that xenon binds to the protein. Under 10 atm gaseous xenon and in the absence of substrates more than 60% native enzyme is converted into Cu(I)-semiquinolamine radical species, showing for the first time that both monomers in the dimer can generate the radical. Under the same experimental conditions the copper-free lentil enzyme is able to generate an intermediate absorbing at about 360 nm, which is assigned to the product Schiff base quinolaldimine which, to the best of our knowledge, has never been observed during the catalytic mechanism of plant amine oxidases. A possible role of the lysine residue responsible for the formation of Cu(I)-semiquinolamine and quinolaldimine, is proposed.
Mechanism-Based Inactivators of Plant Copper/Quinone Containing Amine Oxidases
Phytochemistry, 2005
For Abstract see ChemInform Abstract in Full Text.
Inhibition of Copper Amine Oxidase by Haloamines: A Killer Product Mechanism
Biochemistry, 1997
The observation that the alkylamines 2-Br-ethylamine and 2-C1-ethylamine and 1,2-diaminoethane, t... more The observation that the alkylamines 2-Br-ethylamine and 2-C1-ethylamine and 1,2-diaminoethane, the shortest diamine, are irreversible inhibitors of several copper amine oxidases led to the investigation of the mechanism by which these compounds react with the highly active amine oxidase from lentil seedlings. 1,2-Diaminoethane, 2-Br-ethylamine, and 2-C1-ethylamine were found to be both poor substrates and irreversible inhibitors of lentil amine oxidase; inactivation took place in both the presence and absence of oxygen. All three compounds strongly affected the spectrum of the enzyme, leading to the formation of a stable band at 336 nm both in anaerobiosis and in aerobiosis, consistent with an interaction with the enzyme cofactor 6-hydroxydopa. On the contrary, the corresponding propylamine compounds 1,3-diaminopropane, 3-Br-propylamine, and 3-C1-propylamine were reversible inhibitors of lentil amine oxidase. Inhibition was shown to be due to the aldehyde oxidation products rather than the short chain amines themselves; a reaction mechanism is presented which involves attack of the aldehyde on the 6-hydroxydopa-derived free radical catalytic intermediate. With 1,2-diaminoethane, 2-Br-ethylamine, and 2-C1-ethylamine, the complex produced will form a stable 6-membered ring, causing irreversible inhibition of the enzyme.
Phytochemical Analysis, 1998
Copper amine oxidase was shown to be able to oxidize kynuramine to the corresponding aldehyde, wh... more Copper amine oxidase was shown to be able to oxidize kynuramine to the corresponding aldehyde, which spontaneously rearranged to 4-hydroxyquinoline. Under anaerobic conditions, the native enzyme oxidized one equivalent of kynuramine and released one equivalent of aldehyde per enzyme subunit. The apoenzyme gave exactly the same 1:1:1 stoichiometry under anaerobic as well as aerobic conditions. These findings demonstrate unequivocally that copper-free amine oxidase can oxidize substrates with a single incomplete turnover. # 1998 John Wiley & Sons, Ltd.
Journal of Protein Chemistry, 2000
The oxidation of L-ornithine and L-arginine catalyzed by lentil (Lens esculenta) seedling copper-... more The oxidation of L-ornithine and L-arginine catalyzed by lentil (Lens esculenta) seedling copper-amine oxidase has been investigated by polarographic techniques, optical spectroscopy, and capillary electrophoresis. Both L-ornithine and L-arginine were found to be poor substrates for lentil amine oxidase. L-Ornithine was oxidized to glutamate-5-semialdehyde and ammonia, in similar manner as usual substrates. Glutamate-5-semialdehyde spontaneously cyclizes to Δ1-pyrroline-5-carboxylic acid. Arginine is oxidized by an unusual mechanism yielding glutamate-5-semialdehyde, ammonia, and urea as reaction products.
Journal of Protein Chemistry, 2001
Copper/TPQ amine oxidases from mammalian and plant sources have shown many differences in substra... more Copper/TPQ amine oxidases from mammalian and plant sources have shown many differences in substrate specificity and molecular properties. In this work the activity of lentil seedling amine oxidase was followed at various temperatures in 100 mM potassium phosphate buffer, pH 7, using benzylamine as substrate. The discontinuous Arrhenius plot of lentil amine oxidase showed two distinct phases with a jump between them. Thermal denaturation of the enzyme, using differential scanning calorimetry under the same experimental conditions, showed a transition at the same temperature ranges in the absence of substrate, indicating the occurrence of conformational changes, with an enthalpy change of about 175.9 kJ/mole. The temperature-induced changes of the activity of lentil amine oxidase are compared with those of bovine serum amine oxidase (taken from the literature).
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Papers by Alessandra Padiglia